Cnidaria By: Michael Dang Annie Ma David Shia http://scrapetv.com/News/News%20Pages/usa/images-3/Nomura-jellyfish-3.jpg
Phylum Phylum: Cnidaria Families: • Hydrozoa- polyp and medusa stages in reproductive cycle (Ex: corals) • Scyphozoa- reduced polyp stage (Ex: jellies) • Cubozoa- box shaped polyps (Ex: box jellies) • Anthozoa- no medusa stage (Ex: corals)
Sample Animals • Jellyfish • Corals • Hydras • Box Jellyfish • Anemone • Sea Wasp • Sea Pens • http://www.biology4kids.com/misc/photos/cnidaria1.jpg
Body Cavity • Single Body Cavity diploblastic (two membranes: ectoderm/endoderm) used for digestion and respiration • They contain one cavity that operates as both their mouth and anus • Polyp- mouth cavity is on top • Medusa- mouth cavity is on bottom
Body Symmetry • Radial Symmetry http://www.uic.edu/classes/bios/bios100/labs/radial.jpg
Nervous System • Cnidaria lack a brain and a central nervous system, but they do have a net of neurons • Ocelli: organs that sense direction of light • Statocysts: means of regulating tilt and acceleration in cnidaria
Circulatory System • None
Digestive System • All are carnivorous • Absorb nutrients by filtering water • Tentacles put the prey into the mouth where digestive enzymes are used to break prey down into organic substances
Excretory System • Present • Anus/ mouth • Diffusion
Locomotion/ Musculature • Has muscle, but really weak in most Cnidaria. Strong enough to direct movement in a current • Jet Propulsion: water is squeezed and then released from the cavity using coronal muscles • Some sea anemone can creep along
Skeletal Type • Cnidaria bodies are composed of the jelly-like substance called mesoglea • Most can form a hydrostatic skeleton, in which the cavity fills with water, expanding the body of the cnidaria • Coral have exoskeletons composed primarily of calcium http://biology.unm.edu/ccouncil/Biology_203/Images/SimpleAnimals/cnidariaDiagram.jpeg
Sensory Structures/ Features • Simple sensory structures • Responds to touch through cnidocytes, stinging cells located on the tentacles • Nematocytes, the stinging capsule of a cnidocyte, releases a poisonous thread when triggered by a chemical or touch http://kentsimmons.uwinnipeg.ca/16cm05/16labman05/lb5pg2_files/cnidocyte.gif
Reproduction • Sexual and asexual reproduction • Cnidaria usually have 2 main forms in their life cycle: the polypoid stage is diploid, and the mature polyp is usually found in colonies. Medusae are produced asexually through budding, which reproduce sexually to form polyps. http://www.palaeos.com/Invertebrates/Cnidaria/Images/obelia_cycle.gif
Gas Exchange • Cnidarians lack the organs for gas exchange, so they just let the gas from the water diffuse through their bodies
The amount of poison from a sea wasp, a cubozoan, is powerful enough to kill 60 people! Coral is really a colony of really small polyps! Many species of jellyfish are bioluminescent! Other
QUIZ TIME • What are the two forms of a Cnidaria’s life cycle? • Polyp and Cnidocyte • Medusae and Polyp • Polyp and Hydrozoa • Cubozoa and Medusae • None of the above
Answer B • Medusae and Polyps • Medusae= tentacles facing down. Motile. • Polyp= tentacles facing up. Stationary.
QUIZ TIME 2. What mechanism do Medusae use to move through the water? • Current • Jet Propulsion • Latching on to other animals • A and B are both correct • All of the above
Answer D • Current and Jet Propulsion • Medusae have relatively weak muscles, so they must use the current to help them move • Jet Propulsion= uptake and release of water to create the thrust force to make them move forward.
QUIZ TIME 3. What is the Mesoglea? • The excretory waste of the Cnidaria • The nervous system of the Cnidaria • The name of the colonies that the polyps form • The tentacles of the jellyfish • The substance that the Medusae’s body is composed of
Answer E • The substance that the Medusae’s body is composed of
QUIZ TIME 4. What systems are absent in Cnidaria? • Skeletal and Nervous • Excretory and Digestive • Nervous and Circulatory • Circulatory and Digestive • Musculature and Reproductive
Answer C • Nervous and Circulatory • Cnidaria have no brains, thus no nervous system, but do have a simple sensory network throughout the body. • They do not need a circulatory system and regulate substances through diffusion.